Interpretive Summary: Lack of product consistency is a problem with beef. Composite breeds of cattle are similar to their contributing purebreds in phenotypic co- efficients of variation and in genetic variation for production traits. Estimates of heritability for production traits are similar in composites and their contributing purebreds. Estimates of heritability for calving difficulty score and percentage calving difficulty are higher in calves with 2 yr old dams than with dams equal to or greater than 3 yr old. Herit- ability of calving difficulty score is sufficiently high (.33) for calves with 2 yr old dams to be a useful selection criterion for reducing calving difficulty. The genetic correlation between birth weight and calving difficulty score is higher in calves with 2 yr old dams (.59) than between birth weight and 368-d weight (.33). Thus, there is opportunity to reduce calving difficulty score by reducing birth weight while maintaining 368-d weight.

Technical Abstract:
Genetic and phenotypic parameters were estimated for growth, reproductive, and maternal traits for both the individual and dam for 9 purebreds and 3 generations of 3 composite populations to which the purebreds contributed. Phenotypic coefficients of variation and genetic standard deviations were not different between composites and contributing purebreds. Generally, estimates of heritability did not differ among all breed groups combined, contributing purebreds combined, and composites combined. Estimates of heritability for calving difficulty score are sufficiently high (.33) to be a useful selection criterion for reducing calving difficulty. The higher genetic correlation between birth weight and calving difficulty score (.59) in calves with 2 yr old dams than between birth weight and 368-d weight (.33) suggests opportunity to reduce calving difficulty by reducing birth weight while maintaining 368-d weight. The heritability of reproductive traits was low and the heritability of traits analyzed as traits of the dam was lower than heritability of traits analyzed as traits of the individual.